Electrical transmission of pictures



De. 30, 1930. cf-A. HoxlE 1,787,273

ELECTRICAL TRANSMISSION OF "PIcTUfiEs Original Filed Sept. 23, 1924 4 Inventor: Char-lea Ahoxte, by

Hts Attorney.

- CHARLES A. HOXIE, OF SCEENECTADY, NEW YORK, ASSIGNOR 'I'O GENERAL ELECTRIC Original application filed September 23, 1924, Serial No. 789,428, new Patent No. 1,648,687, dated November Patented Dec. 30, 1 930 UNITED STATES.

.PATENT OFFICE 7 COMPANY, A CORPORATION OF NEW YORK ELECTRICAL TRANSMISSION OF PICTURES 8, 1827. Divided and this-application filed March 23, 1927. Serial No. 177,684.

My invention relates to the electrical transmission of pictures, and has for its principal object the provision of an improved apparatus and method of, operation which may be I. utilized to transmit pictures and views either by wire or by radib.

This application is a division of my copending application, Serial No. 739,423, filed Sept. 23, 1924, Patent No. 1,648,687, and is assigned to the same assignee as the aforesaid copending application.

My invention will be better understood from the following description when considered in connection with the accompanying drawings andits scope will be pointed out in the appended claims.

Referring to the drawings, Fig. 1 illustrates an apparatus wherein my invention has been embodied; Fig. 2 illustrates a modified form of transmitting apparatus; Figs. 3 and 4 relate to the operation of the apparatus. i

Fig. 1 shows a transparent drum 1 which is arranged to be surrounded by the transparency comprising the picture to be transmitted. Aphoto-electric cell 2 is mounted within the drum 1 which is arranged to be rotated and moved slowly along the axis of its rotation by means of a motor 3 coupled to it througha shaft 4, a worm 5 and a gear 6 which is splined to a sleeve 7 threaded on a stationary rod or support 8. Adisk 9 provided with a series of openings 10 and a series of'openings 11 is mounted on the shaft 4. Light from a. suitable source 12 passes through the perforations 10 and is focused by a lens 13 at'a small opening 14 in a screen 15 which surrounds the cylinder l and cell 2. From the-opening 14, the light passes through the transparency into the windowpf the cell 2. The perforated disk 9 functions as a chopper to produce a'carrier wave which is modulated by variation in the light transmitted through the transparency to the photo electric cell.

The disk 9 is also utilized to producea synchronizing wave whereby synchronism is maintained between the transmitting and receiving apparatus of the system. In producing this synchronizing wave, light from a source 16 is caused to pass through the openelectric cell 18.

ings 11, a lens 17 and the window of a photo- The current transmitted through the cell 2 and the currenttrsmsmitted through the cell 18 is supplied to an amplifier comprising a space discharge device 21 and a transformer 22. The secondary circuits of the transformers 20 and 22 are provided with terminals 23 which may be connected either to the receiver or to an antenna through which the carrier and synchronizing waves are broadcast.

The modulated carrier current is received by an apparatus comprising a space discharge device 24, a transformer 25 and a capacity 26 provided for turning the secondary circult of the transformer 25 to the frequency at which the carrier current is transmltted. An electromagnet 27, connected in the secondary circuit of the transformer 25, is arranged to rock.

a shaft 28 and a mirror 29 mounted on this shaft. This shaft and mirror are shown in my Patent No. 1,456,595, May 29, 1923. It should be understood that the armature of the electromagnet 27-may have any other suitable form such as a circular diaphragm or the like.

In the operation of this part of the receiving apparatus, light from a source 30 having a .line filament is transmitted through 'a lens 31 to the mirror 29'from whence it is reflected to a cylindrical lens 32 by which the line image of the source 30 is contracted to a spot and projected on an opening 33 in a screen 34;

A drum 35 for supporting a sensitized stri or,film is mounted within the screen 34 an is arranged to be rotated and to be moved is supplied through a space discharge device 42 and a transformer 43, acapacity 44 being provided for turning the secondary circuit device 45 in the primary circuit of the trans-.

former 22 is arranged to be opened by enm gagement with a pin 46 on the drum 1. Engagement of the pin 46 with the contact device 45 temporarily interrupts the circuit of.

the transformer 22, thus causing an electrical impulse to be applied to an electromagnet 123 through which the clutch 37 is released .and permitted to move into its closed position. When this occurs, the receiving drum 35 starts to rotate. V

The frequency of the carrier wave for the go picture is determined by the rate at which the openings 10 in the disk 9 are moved past the light source 12, and the amplitude of this car- ,rier wave is varied in accordance with the shade of the parts of the picture which are moved past the opening 14. The carrier wave for synchronizing the receiving apparatus has 'a constant frequency which is dependent on the rate at which the "openings 11 of the disk 9 are moved past the light source 16. As previously indicated, the secondary circuit of the receiving transformer 25 is tuned to 'the frequency of the picture carrier wave and the secondary circuit of the transformer 43 1S tuned to the frequency of the synchronizing carrier wave.

The lightsource 30 at the receiving. station is located below the opening 33 in the screen 34. and,'as the shaft 28 rocks on its horizontal axis, vibrations of the mirror 29 cause the reflecteddight beam to form a vertical illuminated streak on the casing 34 extending through the opening 33. Were the screen 34 removed during the transmission of a picture, the light image for a partial rotation of the drum 33 might resemble what is shown in Fig. 3. 'Here, the darkest or most exposed'portions 47 correspond to the times of minimum vibratory movement of the light beams while the lightest or least exposed portions 48 correspond to the times of greatest vibratory movement of the beams.

It will be remembered that the amplitude of In Fig. 4,,the dark portions 49 correspond to the portions 47 of Fig. 3 and the light pork tions 50 correspond to the portions 48 of cell for producing carrier waves of different Fig. 3. Various intermediate gradations of course appear depending on the amplitude of. the vibrations of the light beam.

In the "modified form illustrated by Fig. 2, the-synchronizing wave is produced by an alternating current generator 51, which takes the place of the photo-electric cell 18 OfFig. 1-. A chopper 52 is provided for interrupting the light transmitted to the photo-electric cell 2 and producing the carrier wave whereby the picture is transmitted.

The embodiment of the invention illustrated and described herein has been selected for the purpose of clearly setting forth the principles involved. It will be apparent, however, that the invention'is susceptible of being modified to meet the different conditions encountered in its use and 'I therefore aim to cover by the appended claims all modifications within the true spirit and scope of my. invention.

What I claim asnew and desire to secure by Letters Patent of the United States is 1. The combination of a movable member adapted to support a light sensitive member, a screen arranged to surround said movable member and provided with a small openin through which successive small areas of sai light sensitive member are adapted to be exposed, a light source arranged to produce a beam of light alined with said opening when at rest, and means arranged to vibrate said beam lineally and to produce on said screen an illuminated band which includes said openin-g and extends on opposite sides thereof.

2. A picture transmitting apparatus comprising means for producing impulses whose amplitude varies in accordance with: the illumination of successive unit areas of the picture to be transmitted, a movable light sensitive member, a screen provided with a small opening and arranged to surround said light sensitive member, means for directing a beam of light toward said screen, and means for causing said beam to vibrate rapidly across .110 said opening with an amplitude substantially proportional to that of said im ulses wherebysuccessive-portions of the light sensitive member are illuminated by light which varies in intensity inversely as the shading of the successive unit areasof the picture.

3. The combination of a picture transmitting apparatus comprising aplurality of photo-electric cells, a plurality of light sources each arranged to illuminate the window of a different one of said cells, a movable member provided with openings difi'erently spaced in'separate rows each arranged to be moved between a different source and frequency, and means for modulating oneof said waves in accordance with the shade of a picture to be transmitted.

4. The combination of a picture receiving apparatus, and a picture transmitting appa- 130 ratus comprising a plurality of photo-electric cells, a plurality of light sources each arranged to illuminate the window of a difiercut one of said cells, a movable member pro- 5 vided with openings differently spaced in separate rows each arranged to be moved between a difl'erent source and cell for'producing carrier waves of different frequency, means for modulating one of said waves in accordance with the shade of a picture'to be transmitted, and means arranged to respond to another of said waves for maintaining syn-' chronism between said transmitting and receiving apparatus.

5. In picture transmission apparatus wherein the transmitted impulses vary in amplitude in accordance with the shade of the successive unit areas of the picture being transmitted, means adapted to rotatably supze port a light sensitive member, a screen having a small opening therein in front of said member, a source of light, means for directinga beam therefrom toward said screen and means responsive to the amplitude of said'impulses for causing said beam to vibrate over said opening past the opposite sides thereof. In Witness whereof, I have hereto set my hand this 22nd day of March, 1927.

CHARLES A. HOXIE. 

